In recent years, the existing alternating magnetic field sensing technical solutions, such as coils where the higher the frequency, the higher the sensitivity, have difficulty in sensing a magnetic field with lower frequency. Furthermore, it is easily affected by high-frequency interference, and sensing weak signal needs coils of a large size. Hall devices and magnetic resistance devices can sense a static magnetic field. Although static magnetic field signals can be removed by a high-pass filter, the sensor, in the presence of a magnetic environment, requires a very large dynamic range for sensing a weak magnetic field change.